(1) Field of the Invention
This invention relates to a method and apparatus for cooling systems and, more particularly, to a multi-stage hybrid evaporative cooling systems.
(2) Description of Related Art
The power degradation curves of most power generating systems are such that as the temperature of air increases, the output power of these power systems decreases due to a decrease in the density of the air. In other words, most power generating systems require an intake of dense air for a more efficient operation in terms of greater power output. That is, the denser the air, the greater the operating efficiency of the power generators. It is well known that cooler air is denser than warmer air, and hence, today's power generating intake systems are generally coupled with air cooling systems, which provide the power generating units with cooler, and hence, more denser air for a more efficient operation of the power units. Therefore, it could be said that the cooling systems indirectly function as power augmentation systems for power generating systems by increasing their efficiency, and hence, their output power.
Traditional methods for providing cooler denser air to increase overall power generating efficiency include steam injection, refrigeration, fogging, and direct evaporative cooling of air. A less expensive approach to increasing the intake air density by cooling, other than these conventional methods, is an indirect evaporative approach. Prior patents in this area include Schlom et al.: U.S. Pat. Nos. 4,023,949; 4,107,940; 4,137,058; 4,156,351 and 4,418,527; Fogelman: U.S. Pat. No. 5,076,347; and Kopko: WO9851916A1.
A recently developed method for cooling air is the hybrid evaporative cooling system (known as the “Schlom” cycle) disclosed in the U.S. Pat. No. 6,385,987 to Schlom et al., which may be used as standalone air cooler or with different power generating systems. The entire disclosure of the U.S. Pat. No. 6,385,987 to Schlom et al, issued May 14, 2002, is incorporated herein by this reference, and the information incorporated herein is as much a part of this application as filed as if the entire text and drawings of the U.S. Pat. No. 6,385,987 were repeated in this application, and should be treated as part of the text and drawings of this application as filed.
The heat exchangers disclosed in U.S. Pat. No. 6,385,987 are useful for both single and multiple unit indirect evaporative processes. The evaporative apparatus for cooling comprises both a multi-stage indirect evaporative cooling heat exchanger, and a multi-stage sump where each sump stage, in a one-to-one relationship with a stage of the multi-stage heat exchanger has sump water at progressively cooler temperatures as air progresses further into the heat exchanger. Because there are separate, and completely sealed and isolated stages of the heat exchanger and the water sumps (creating thermal isolation between the stages), progressive cooling is induced on dry side output air. Other multistage heat exchangers with their associated multistage sumps can be combined, with the cooled air of a first multistage evaporative assembly feeding into the intake end of a second multistage evaporative assembly, and so on, with each sealed stage of the multistage assembly being thermally isolated.
Areas in which additional increased efficiency of the hybrid evaporative cooling system disclosed in the U.S. Pat. No. 6,385,987 might be improved include a better heat exchange and coolant evaporation processes, and the use of a novel refrigeration processes, bringing the “room” inlet dry-bulb temperature as close as possible to the exhaust air wet-bulb temperature so as to increase the thermodynamic efficiency of the actual process.